get a service and ask for a transmission flush and fluid change with the factory reccomended fluid...
This usually helps with holdens and mitsubushis.....
A retro fitted transmission fluid cooler would DEFINITlY help with prolonging the life of the trans.
You can get one from a falcon or commodore pretty cheaply from the wreckers( like $20, then $5 of hoses and clamps), make sure there arent any major dents or kinks in the piping, and clean it out with some additive(let it soak in a tray) and rinse...
Mount it in front of the radiator with about 10 com gap so air can circulate properly,
Look at a pintara Ti at a wreckers to see how the hoses connect... i THINK the Ti has a trans cooler built into the radiator im pretty sure,( ive had one for 3 days...) so it still heats up a hell of a lot!
Im going to get a remote mounted one myself, I will post up some pics when its done...
You say it happens when cold, maybe a cooler wont do anything... so just find out the correct fluid to use, and get the trans flushed and fill it with the right stuff!!!